I have a 1988 Holden Astra SLX but no handbook.  Being a 61 year old on limited income I would like to replace the front disc brake pads myself if possible. Is anyone out there kind enough to give me a run down on how to do this?

Go to Repco with the cars details, make\model\year, and order if not in stock.
To get at the brakes you need to jack the car up and remove the wheel, on the caliper there are 2 bolts on the back of it, they are some times very tight so you will need the correct sized spanner to get them undone.
With the bolts out, you will be able to slide it off the disc, you dont need to take off the brake line but you have to be careful dont drop it. With the old pads still in, use a bar to prise them apart and make the gap as big as possible so the new pads with fit on the disc, when doing this you are forcing the brake fuild back into the sysrem so it takes awhile, make sure everything is clean of brake dust and the pistons arent leaking, then put the new pads in the same configeration as the old ones, put the caliper back on, insert and tighten bolts as tight as you can MUST BE TIGHT!! Replace wheel.
In the car pump the brake pedal a few times and see that the car actually stops before you then drive for 500mts with the brakes slightly on to bed them in.

I take no responsibility for your use of these instructions.

If you have to ask this question, you should not be doing it yourself. Brakes are one of the most important parts of the car and should be worked on by a MTA registered mechanic.
You won't save a great deal by doing it yourself as the mechanic can buy the parts at trade price. The small labour cost will be equal to retail price you will pay at the counter.
Also, who can put a price on the peace of mind of knowing your car will keep you safe and alive.